1. Field of the Invention
The present invention relates to a projection display device, which separates white light from a light source into three-color lights of red, blue and green, modulates these color lights through a light valve composed of a liquid crystal panel or the like in response to image information, and recombines the modulated lights with an optical combining means to enlarge and project an image onto a projecting surface through a projection means.
2. Description of Related Art
A mechanism for fixing a light valve onto a prism body which is an optical combining means for a projection display device is disclosed in Japanese Patent Laid-Open Publication No. Hei 6-118368. In this fixing mechanism, the light valve is directly fixed onto the light incident face of the prism body with an adhesive.
The use of such a mechanism permits the omission of a pixel alignment mechanism between a plurality of light valves, which modulate the light which is particularly separated into red, green and blue, and a focussing mechanism, which adjusts the position of the formation face of each image which becomes an object within the focal depth of a projection lens. Accordingly, miniaturization and weight reduction of the optical system and reduction of the number of parts can be achieved in a projection display device.
However, when the light valve is directly bonded and fixed to the light incident surface of the prism body, it involves the following problems to be solved.
First, external light which enters from the external part of the device enters the light valve, there may be a possibility that each element may be operated by mistake. Moreover, direct handling of the light valve may cause its breakage, and this is not desirable. For example, direct chucking of the light valve, for bonding the light valve by a jig to the prism body may cause breakage at the edge, corner or the like of the light valve. Further, because the light valve is easily affected by static electricity, direct contact of the light valve for bonding it to the prism body is not desired.
In the light valve bonded to the prism body, part of the pixels may develop defects or the like as time passes by and the light valve changes. A light valve having defects must be replaced with a new one. However, it is difficult to exchange the light valve with defects with a new one since it is bonded and fixed to the prism body. It is not easy to detach the bonded and fixed light valve without damaging the light incident face of the prism body. Because of this, there are cases, for example, when exchanging the light valve with defects including the prism body, and this is not economical.
Furthermore, when the light valve is directly bonded and fixed to the prism body, the linear expansion coefficient of the light valve and the prism body are different so that thermal distortion may occur.